What causes stormwater runoff?

Roofs, driveways, sidewalks, roads-- housing developments are full of surfaces that do not absorb water. These impermeable surfaces can cause problems with stormwater management. A natural prairie has plants with deep roots and thick topsoil that absorbs much (if not all) of the rain during a Kansas thunderstorm; contrast this to a housing development, where much of the surface area absorbs little (or no) stormwater. The increased runoff from impermeable surfaces can cause headaches for homeowners, who have to deal with flooded basements, cracked foundations and costly repairs.  

During a 1" rainstorm, a house with a 2000 square foot roof will have over 1000 gallons of water running off of it! That's a lot of water, especially if it comes shooting out of a neighbor's downspout aimed at your property.

What are the consequences of increasing stormwater runoff?

By increasing the amount of impermeable surfaces in the Kansas River watershed, developments can increase the chance of floods. Without proper planning, there is the potential for creating a dangerous situation for flood prone communities. This is one of the biggest reasons to carefully manage stormwater runoff.

But there are other important reasons as well. Like drinking water. Stormwater runoff entering storm drains makes its way to streams, reservoirs and eventually the Kansas River itself. Many communities obtain their drinking water directly from these sources. This means that  pollutants carried by runoff into surface waters will have to be removed by municipal water treatment plants, potentially increasing your water bill.

What causes sedimentation in our reservoirs?

Poor construction practices can greatly increase the amount of sediment in runoff. 

This is important, since sedimentation is a major problem in the Army Corps of Engineers flood control reservoirs on the Kansas River system. These reservoirs were built to hold back stormwater and reduce the amount of flooding in downstream communities. But now we are finding that soil particles washed into streams during storms are causing sedimentation in Clinton, Perry and Tuttle Creek Reservoirs. The big federal reservoirs on the Kansas River are rapidly filling in with sediment, which reduces their storage capacity. When this happens they are not able to hold back flood waters.

They are also unable to store sufficient amounts of drinking water for our growing communities.

These two problems are an important concern, and the Kansas Water Office funds many projects to reduce sedimentation in Kansas streams and rivers, and hence in the reservoirs. These projects attempt to cut off the problem at the source-- stormwater runoff. This is one of the reasons why the Johnson County Stormwater Management Program has adopted a series of Best Management Practices for Home Builders.

What is pollution from runoff?

Stormwater washes fertilizer, herbicides, and pesticides off of lawns. Fertilizers increase nutrients in reservoirs, leading to algal blooms and "skunky" tasting water and expensive water treatment problems for municipalities.

Incorrect or excessive use of pesticides and herbicides by home owners leads to pollution in the Kansas River and has caused the Kansas Department of Health and Environment to issue health warnings. A good example of this was the fish consumption advisory that was in place for many years between Lawrence and Eudora because of contamination by Chlordane, a pesticide used in homes to prevent termites. The Chlordane advisory has recently been lifted, although a PCB advisory is still in place. (Click here for more information about current fish advisories in the Kansas River.)

What can you do to help?

In the next two sections we discuss some of the things you can do to reduce stormwater runoff and improve the quality of water running off of your homes and yards. We also discuss requirements for managing stormwater in housing developments under Johnson County's Stormwater Management Plan. Working together we can protect our homes from flooding and make sure that we always have good, clean and abundant drinking water supplies.